Think Outside The Row

University of Nebraska agronomists have been comparing yields from corn planted in every row (solid planting) with each of the following three planting patterns: Plant one row and skip one row; plant two rows and skip one; and plant two and skip two.

Soil moisture in the skipped row or rows is held in reserve for later use by the corn crop, says Bob Klein, University of Nebraska agronomist. Corn roots haven't reached into this skipped zone until later in the season.

The bar graph on page 48 illustrates the outside-row effect from Iowa State University research.

Obviously, skip-row planting is a practice for corn production in non-irrigated areas where rainfall is often very yield-limiting, especially in the later part of the season. Nebraska, western Kansas and eastern Colorado are where skip-row trials have been conducted by Nebraska researchers who refer to corn in these trials as “rain-fed” corn.

University of Nebraska trials, which began on a limited scale in 2003, have shown: Plant two-skip two plantings generally out-yield solid-planted corn when solid planted corn yields are under 90 bu./acre. Yields have usually been about equal between solid plantings and plant two-skip two at yields up to 120 bu./acre. And, yields have been about equal between solid plantings and plant two-skip one at up to 130-140 bu./acre.

All trials are with mid-season hybrids for the area, planted in 30-in. rows, according to Klein, at the University's West Central Research and Extension Center (WCREC) at North Platte.

At Trenton, NE, in 2005, a severe moisture-limiting year for that site, all three skip-row patterns (plant two-skip one, plant two-skip two and plant one-skip one) at plant populations of 10,000, 15,000 and 20,000/acre out-yielded their solid-planted counterparts. The plant two-skip two pattern at 20,000 plants/acre performed best, out-yielding solid-planted corn in 30-in. rows at that population by 40 bu./acre — 84 vs. 44 (see accompanying bar graph of yields).

In-row plant spacing in the planted rows of a skip-row system are, of course, planted at a higher density within the row to get the same number of plants per acre as you would in solid plantings. For example, getting 12,000 plants/acre in a plant two-skip two planting requires in-row plant spacing equal to the spacing for 24,000 plants/acre in an every-row planting.

North Platte plots in 2006 received adequate rainfall. And, yields from skip-row plots were not consistently better than their solid-planted counterparts, preliminary results show.

The highest yield among all North Platte plots for 2006 was 132 bu./acre, which came from a plant one-skip one plot. Plant population was 20,000/acre (an in-row plant spacing equivalent to 40,000/acre in conventional planting). Conventional planting at 20,000 plants per acre yielded 115.2 bu./acre.

At the Trenton plots in 2006, the best skip-row yield was 125 bu./acre from a plant two-skip two plot. Population was 20,000 plants per acre (an in-row equivalent spacing of 40,000 plants/acre in conventional planting). The best conventionally planted plot yield at Trenton was 117.1 bu. from a plant population of 20,000.

All yields are corrected to 15.5% moisture.

“I think there's an advantage in crowding plants like that (40,000 in-row spacing in skip-rows),” Klein says. The plants are forced to compete, which helps them tap into the unplanted zone for moisture later in the season, he adds.

Reducing the optimum population by about 20% in skip-row planting may be possible, especially with the high price of seed corn, Klein says. “We need to do additional research on plant population in skip rows.

“I like the plant two-skip two to get maximum drought tolerance,” he says. In the event of good growing conditions, that pattern may not be able to capitalize as fully as plant two-skip one, but it offers more drought tolerance in dry years, he says.

While the studies have been mostly on finer-textured soils, says Klein, “we think skip-row can even work on the sands.”

Skip-row planting is about more than just leaving unplanted rows interspersed with planted ones. It's for no-till systems, especially an ecofallow system.

In ecofallow, the program begins with a wheat crop followed by one to two years of skip-row corn. “To really make the system work, you need to produce a good winter wheat crop,” Klein says. That means the right wheat variety, fertilizing based on soil tests, a good weed control program and leaving as high a wheat stubble as possible — even leaving a few heads if necessary — and spreading straw and chaff as uniformly as possible for corn planting the following spring. Klein likes the idea of a stripper head to leave as much wheat stubble as possible.

Using gauge wheels narrower than the standard ones on planters to limit residue flattening during planting would be helpful. Klein says, “We want to keep as much of that residue standing as we can. That's like money in the bank.”

A fall application of atrazine, along with a contact herbicide, not only controls moisture-sapping weeds in the stubble after harvest, it eliminates volunteer wheat plants, which can become hosts for the wheat curl mite that can transmit wheat streak mosaic to adjacent fields planted to wheat that fall.

Consider a pre-emerge herbicide ahead of corn planting in the spring. In many cases, a two-thirds label rate of pre-emerge herbicides, such as an atrazine-Balance combination, can do the job. But be aware that chemical companies won't stand behind their products when used at reduced rates. If grassy weeds could be a problem, consider a pre-emerge grass herbicide application, Klein says.

A good thing about skip-row planting is that it requires no additional machinery investment. In fact, for those with six-row planters, it's like having an eight-row planter in a plant two-skip two pattern: The two middle row units don't plant, and you leave a two-row width between planter passes.

Ideally, where you plant corn after corn, you try to plant in the previous year's non-planted rows, Klein says.

Phosphorus is row-banded with the planter. Nitrogen applications are UAN, which are often used as a carrier for the herbicide. Applying it ahead of planting improves the opportunities for rainfall to move the nitrogen into the soil profile.

Klein notes that corn hybrids now have improved tolerance to cold and dampness associated with no-till systems in April plantings. “I like seed treatment for this system,” he says.

Insurance Coverage

The Farm Service Agency and Federal Crop Insurance Corporation are continuing to rule for 2007 that skip-row fields will not be considered 100% planted for acreage history or crop insurance purposes. For example, a field planted in a pattern of two planted rows and two skipped rows on row spacings of 30-40 in. will be considered only 50% planted. Only 50% of the acres in that field can be insured. In a plant two-skip one pattern on 30- to 40-in. rows, only 66.67% of the acres can be insured.

As in the past, federal crop insurance coverage on skip-row plantings can be insured only by special written agreement.